Section insulator



Nov. 12, 1940. c. c. WHITTAKER SECTION INSULATOR Filed June 28, 1938 INVENTOR Charles C Whittaken ATTOR Y Patented Nov. 12, 1940 UNITED STATES PATENT OFFICE SECTION INSULATOR Pennsylvania Application June 28, 1938, Serial No 216,249

5 Claims.

My invention relates, generally, to trolley systems and it has particular reference to section insulators for use in overhead trolley systems.

Heretofore, where section insulators, used in 5 overhead trolley systems, have comprised insulating members provided with internal metallic strain members for increasing the tensile strength of the section insulator, it has been customary to utilize strain members which rely 10 upon the interlocking relation of portions of the members for maintaining them in fixed relation within the insulating material. I have found, however, that a difierent construction may be used to advantage wherein there is no actual interlocking relation between the strain members, which are instead retained in fixed spaced relation with each other by the use of an entirely diiferent principle of load stress distribution within the insulator member.

It is, therefore, generally an object of my invention to provide a reinforced section insulator for overhead trolley systems, wherein the reinforcing or strain members have no interlocking parts.

More specifically it is an object of my invention to provide a section insulator having metallic strain plates secured therein in fixed relation solely through the resistance to shear of molded insulating material associated with the members.

Another object of my invention is to increase the tensile strength of a section insulator by using spaced apart, perforated, metallic strain plates molded in an insulating body for more efficiently distributing the load stresses throughout the insulating material,

A further object of my invention is to utilize the resistance to shear of the insulating material in an insulating member for preventing relative movement of strain plate members formed therein by providing a plurality of portions of the insulating material in interlocking relation with the spaced apart metallic strain plates within the member.

45 Still another object of my invention is to utilize the resistance to shear of a molded insulating material in securing a pair of non-interlocking metallic strain plates in fixed relation in a molded insulator body by providing a plurality of portions of the insulating material having a substantial area resistant to shear, which will be eif-ective to prevent relative movement of the plates.

W A still further object of my invention is to provide ahigh strength, lightweight, reinforced sec- (Cl. 1741S3) tion insulator which shall be simple to construct and durable in service.

Other objects will, in part, be obvious and will, in part, appear hereinafter.

In the practice of my invention, an insulating body member for a section insulator may comprise a pair of non-interlocking metallic strain plates oppositely disposed in spaced relation and provided with a plurality of indentations in the surfaces thereof, about which an insulating ma- 10 terial, comprising preferably a fibrous material impregnated with a resinous binder may be molded in a well known manner by subjecting the assembly to great pressure and applying heat in accordance with the practice of the art, whereby the binder flows throughout the mass of the insulating material which is forced under the pressure into the indentations, to produce an integral union of the plates and insulating material.

For a more complete description of the nature and scope of my invention, reference may be had to the following detailed description, taken in connection with the accompanying drawing, in which:

Figure l is a partly exploded side elevation view of a section insulator embodying the principal features of my invention;

Fig. 2 is a part section View of the insulator of Fig. 1 taken along the line IIII;

Fig. 3 is a cross-section View of the section insulator of Fig. 1 taken along the line III-III;

Fig. 4 is a side elevation view of a metallic strain plate used in practicing a preferred form of my invention; and

Fig. 5 is an end elevation view of the strain plate of Fig. 4.

Referring particularly to Figure 1, the reference numeral Ill may denote generally a section insulator for an overhead trolley system comprising an insulating body member H and end means l2 for securing a trolley wire M to the insulator. A renewable runner member it may be secured on the under side of the insulator in any desirable manner, for example, by an interlocking relation at the ends thereof with the renewable arcing tips lil, so as to provide a renewable wearing surface over which a current collector (not shown) may pass without damage to the insulator body H.

In order to secure both strength and lightness in the insulating member H, I have found it preferable to utilize metallic strain plates 2!! and 22 which may be formed integrally within a mass of insulating material 19 in spaced apart and overlapping relation. As shown in Fig. 4, the similar strain plates 20 and 22 may be provided with a plurality of perforations 24 arranged in any desired configuration, and preferably so that when the strain plates are generally assembled in the insulating material the holes in the plates will be in staggered relation to each other. These plates also may be provided with a roughened surface, such as may be produced by sand blasting or knurling, if desired.

To permit proper distribution of load stresses throughout the section insulator, a pressure plate 26 may be secured to one end of the strain plate in any desirable manner for facilitating connection of the end means l2 thereto. For example, when the strain plate 22 is made from a high tensile strength steel it will be relatively thin, and it hasloeen found desirable to provide a thickened cross-section at the end thereof, to which the end member l2 may be secured, in this instance, by the bolts 21. In this manner, a greater bearing surface may be provided for the bolts 21, so as to effect a more equal distribution of the load stress, in transferring it from the end member I2 and distributing it throughout the insulating material, through the medium of the relatively thin strain plate 22. Thus the pressure plate 26 may comprise a substantially rectangular block of relatively high strength steel which is secured to the strain plate 22 by rivets 28, or some other suitable means, and has holes 29 provided therein for receiving the bolts 21.

In a preferred form of the invention, the strain plates 29 and 22 may be assembled in spaced apart, opposed relation as shown in Fig, 2, with a pad of insulating material 30, which may comprise a fibrous material impregnated with a resinous binder such as Bakelite, sandwiched therebetween. This assembly may then be enveloped by additional insulating material, preferably of a like nature, layers of the impregnated insulating material being, for example, Wrapped thereabout, and the whole placed in a mold and cured by subjecting it to heat and pressure in a manner well known in the art. The resinous binder then flows throughout the insulating material which is sandwiched between the plates and wrapped about them and the insulating material itself is forced into the perforations 24 by the pressure to which the assembly is subjected while in the mold, and the whole becomes an integral mass.

In order to facilitate the positioning of the insulating member in the overhead system under some circumstances, the strain plates may further be provided with aligned perforations 32 in which an insulating bushing 33 may be positioned before the strain plates are subjected to the molding operation. This bushing, as shown more clearly in Fig. 3, then permits the subsequent securing of a supporting lug 34 to the body of the insulator by means of an opening drilled through the insulating member H to accommodate the bolt 36, without decreasing the insulating value of the insulator by short circuiting the metallic strain plates 20 and 22 within the member. Additional insulating value may be given to the completed member by making the bolt holes 29 in the pressure plates 26 sufiiciently large to accommodate insulating bushings 3?, so that the strain plates 20 and 22 will be completely insulated from the end means 12, to which the trolley wire I4 is secured.

When an insulator constructed according to my invention is subjected to a load such as would be imposed upon it in service by the tension of the trolley wire M, the load is transmitted by the end members l2 to the pressure plates 26 through the medium of the bolts 21. From the pressure plates 26, the load is transmitted to the respective strain plates 20 and 22. Any tendency for relative motion of the strain plates, either longitudinally, or rotatively with respect to each other, is then resisted not only by the mass of molded insulation which binds the plates together, but also by the plurality of planes of shear which exist throughout the mass of the insulating material wherever the strain plate and the insulation are associated in interlocking relationsuch as, for example, across the end or ends of a portion of insulation which projects into or through a perforation in one of the plates.

By utilizing in such a manner the relatively high resistance to shear of sections of molded insulation, and preferably molded insulation having a fibrous structure, it has been found possible to construct section insulators of exceptionally high strength for overhead trolley systems, with out any sacrifice of weight or any increase in size. As there are no interlocking portions of the strain plate members in my design, and the load stresses are distributed throughout a large mass of the insulating material, the tensile strength of the insulator may be greatly increased over previous designs by this more efiicient use of the material made possible by my invention. In addition, such insulator construction results in an insulating member having a greatly increased resistance to any bending about a transverse axis, such as is caused by the pull of the trolley wire being applied along the lower edge of the insulator, and, therefore, gives a more serviceable insulator which may be easily and economically manufactured.

It will be realized from the foregoing description that in my invention I have provided a section insulator of the utmost simplicity, wherein there are no interlocking parts of the metallic strain plate members, and wherein the stresses in the insulating body are uniformly distributed throughout almost the entire mass of the insulating material. It may readily be seen that such construction has decided advantages over reinforced section insulators of the prior art, wherein certain portions of the insulating material had to be inserted between the interlocking portions of the metallic strain plates, requiring additional manufacturing operations and increasing the cost thereof.

Since certain changes may be made in the above construction, and different embodiments of the invention may be made without departing from the spirit thereof, it is intended that all the matter contained in the above description, or shown in the accompanying drawing, shall be considered as illustrative, and not in a limiting sense.

I claim as my invention:

1. An insulator member comprising, a pair of relatively thin metallic strain plates positioned in spaced apart and non-interlocking relation and having a plurality of transverse openings therethrough in staggered relation, and an insulating material molded about and between the strain plates under pressure so as to fill the openings and provide an integral mass of insulating material having a plurality of transverse portions within the plates integral with and connecting the insulating material on both sides of the strain plates to hold them together, said plurality of transverse sections of insulating material being subject to shear at substantially the surfaces of the plates to resist relative movement of the plates in substantially the plane of the said plates.

The combination in a section insulator having and means for securing adjacent ends of a trolley wire thereto, of relatively thin flat strain plates of a high strength metal having a plurality of openings therethrough connected to each end means and spacially related in side by side and non-interlocking relation, and a resinous insulating material molded about and between the strain plates to penetrate the openings therein and provide a plurality of projections of insulating material within the strain plates integral with the insulating material on both sides of the strain plates resistant in shear to prevent relative movement of the strain plates in substantially the plane of the plates and connecting the insulating material on both sides of the plates.

3. The combination in a section insulator provided with end means for securing adjacent ends -of a trolley Wire in an overhead trolley system, of

a pair of relatively thin metallic strain plates having a plurality of openings therethrough disposed in spaced side-by-side relation, a resinous insulating material molded about and between the strain piates to interlock therewith in the openings and provide a plurality of separate sections of insulating material in the openings integral with the insulating material on each side of the plates resistant to shear for preventing relative movement of the plates, and a pressure plate associated with each of the said strain plates adjacent opposite ends thereof for effecting a distribution of a load applied thereto, said end means being connected therewith for securing the insulator in the overhead system.

4. In an insulator having end members for positioning the insulator, the combination of a pair of relatively thin spaced apart perforated metallic strain members associated in side-byside relation without interrelating portions, a relatively thick pressure plate secured to an end of each of the strain members for substantially increasing the cross-sectional area of the end and efiecting a distribution of a load applied thereto, and insulating material molded about and between the strain members to penetrate the perforations thereof and provide an integral mass of insulating material having a plurality of integral portions penetrating the perforations and in interlocking relation with the strain members subject to shear at the surface of the members for resisting relative longitudinal motion of the members, said end members being connected to the pressure plates.

5. The combination in an insulating strain member having end members for positioning the member in an overhead trolley system, of a pair of similar relatively thin spaced apart metallic strain plates having perforations in the adjacent faces thereof and positioned in non-interlocking relation, a pressure plate secured to an end or each of the strain plates for providing additional cross-sectional area at the end of the strain plates, and insulating material molded about and between the strain plates under heat and pressure to completely surround the plates and penetrate the perforations so as to provide a plurality of projections of insulating material integral with that surrounding the plates interlocked with the strain plates resistant to shear in preventing relative movement thereof, said end members being disposed in connection with the pressure plate for transmitting a load to the strain plates.

CHARLES C. WHITTAKER. 

